I've noticed this seems to be a common issue, so I'm sharing the steps I took to get email successfully sending (and receiving) using SendGrid with VestaCP and Exim on CentOS 6.

Make sure that your domain is setup and validated in SendGrid and that your DNS/MX records are properly configured (use mxtoolbox.com to scan your domain. it will tell you if you need to fix anything.). It's also a good idea to make sure your reverse DNS is accurate.

EXIM CONFIGURATIONVestaCP replaces exim.conf with its own version that allows it to properly route emails for VestaCP accounts, so it's important to be careful when editing. Best practice is to backup exim.conf file before editing it

@ShaunWHD Hey, thanks for the guide!After I've done the settings, I tested it with mail -s, it was able to send to my email. However, it won't send any notification after doing backups in vestaCP. Is it suppose to send email to my catchall email or admin email?